1. Due to the filter itself:
1. Main engine flushing system: As the filter cloth flushing water uses process water, it is generally not blocked. Filter cake washing water generally adopts process water+filter cloth washing water backwater+vacuum pump circulating water backwater (using water ring vacuum pump), mainly vacuum pump circulating water+filter cloth washing water backwater, and process water is only supplemented occasionally. The content of gypsum in the backwash water of filter cloth is high. Therefore, it is easy to block the filter cake flushing nozzle. The nozzle pressure of the main engine washing system is generally greater than 3kg, and when it is less than this value, the washing effect on the filter cloth cannot be achieved. If the filter cloth is not cleaned for a long time, gypsum will deposit on the surface of the filter cloth and the surface of the filter cloth will be blocked.
2. The distance between the scraper and the surface of the filter cloth is too large, and a large amount of gypsum is deposited on the surface of the filter cloth, which is difficult to clean, and it is easy to scale on the surface of the filter cloth for a long time, resulting in the phenomenon that the surface is not blocked.
3. Sealing performance of the main engine: If the water content of the secondary dehydrated gypsum is greater than 10%, the sealing performance of the main engine should also be considered. Poor sealing performance will lead to the low vacuum degree of the whole system, and the water content of dehydrated gypsum filter cake is obviously high, which will affect the filtration effect. The main reasons for this problem are:
A, vacuum chamber joint degumming, vacuum chamber is generally made of polymer material, which is very elastic and easy to deform. If it is not fixed in time or fixed badly, it may cause vacuum chamber degumming. In this case, only after stopping, put down the vacuum chambers and glue them again to fix each vacuum chamber.
B. There is leakage at the flange joint below the vacuum chamber. There is usually a whistle. To solve this problem, it is necessary to put down the vacuum chamber after stopping the machine, check the gasket, and replace the gasket if there is any problem; If it's not the gasket problem, just tighten the flange bolt at the leak.
C. If the filter main pipe leaks, just tighten the bolts at the leaking place. If there is something wrong with the gasket, it needs to be replaced after stopping the machine. In order to prevent vacuum leakage, it is necessary to test the vacuum degree after system installation and before filter cloth installation. This can control the problem before driving and avoid the trouble after driving.
Second, the reason of the filter cloth itself
1, the quality of filter cloth is determined by its material, weaving technology, interface technology and many other factors.
2. Polyester material: This material is an ideal choice under acidic conditions, with high temperature resistance (the temperature is less than 1-9 at PH value), strong tensile strength, longitudinal and transverse stability and wear resistance second only to nylon.
3. Polypropylene: Good acid and alkali resistance, (ph 1- 13) service temperature is less than 90 degrees, but its tensile strength is not high. Most foreign filter cloth manufacturers do not choose this material. Because the slurry from the absorption tower generally has a ph value of 4-7, and the temperature of gypsum is 70-80 degrees. Dacotex filter cloth in Tan Shi, USA is resistant to high temperature and durable.
4. Weaving technology: the weaving technology of monofilament plus silk and satin blending is widely used in the world. The advantages of this knitting method are smooth surface, rough back and different sizes of front and rear openings. The surface holes are large and the back surface is small, which is easy to intercept solids. The smooth surface makes the surface solids removal efficiency higher. Many polyester filaments of filter cloth manufacturers contain polypropylene instead of 100% polyester material. The filter cloth is affected by the temperature and PH value of gypsum slurry in the absorption tower.
How to clean the clogged filter cloth;
1. For the filter cloth used as alkaline filter material, it needs to be soaked in weak acid solution when cleaning;
2. For the filter cloth used as acid filter material, it needs to be soaked in weak alkaline solution when cleaning.
Soaking time 1 to 2 days. Then clean it up.
Or:
1. high-pressure water gun cleaning;
2. The cloth washer cleans and adds a cleaning agent;
3. Wash with hydrochloric acid or citric acid;
4. Cleaning with caustic soda or hydrogen peroxide;
5. The cloth washing cycle should be determined according to the actual situation, generally not more than 2 months.
Matters needing attention when using filter cloth
1, matters needing attention of belt filter:
① Correctly measure the required filter cloth length (including the joint length).
(2) When sewing, make sure that the weft threads at both ends overlap or are parallel to prevent the filter cloth from escaping during operation.
(3) Pay attention to the operation direction of the interface, so as not to damage or block the filter cloth by blocking the filter cloth interface with the scraper.
2. Precautions for vertical disc machine (vertical disc machine):
① The selected filter cloth should not be too thick, which is not conducive to the sewing of the filter bag when it is installed.
② The surface of the selected filter cloth should not be too smooth, which is not suitable for the formation of filter cake and affects the production efficiency.
3. Precautions for Lauder machine (vertical belt filter):
① The filter cloth requires a certain thickness and strong tensile strength.
(2) The joint shall ensure that both ends of the weft are overlapped or parallel to prevent the filter cloth from running off.
(3) Pay attention to the operation direction of the interface, so as not to damage or block the filter cloth by blocking the filter cloth interface with the scraper.
4, bag filter class matters needing attention:
(1) Don't hang the filter cloth too loosely or too tightly. If it is too loose, it is easy to accumulate dust, and if it is too tight, it is easy to pull it out.
(2) Don't mix old and new filter bags, so as not to damage the equipment at different times.
(3) When replacing the old filter bag, blow it clean with compressed air first, then check whether there are holes, and replace it after it is repaired. If the filter bag is blocked by dust, rinse it with water and dry it for later use.
5. Precautions for wooden headphones:
① When installing the fungus filter bag, avoid hanging hard objects on the filter bag, so as not to damage the synthetic fiber and cause the filter bag to be perforated for a short time.
(2) Stop when the filter cake thickness is appropriate, and then start working after unloading the cake, which can prolong the service life of the filter bag.
(3) When replacing the filter bag, don't buckle the filter bag directly with hard objects, but pull the auxiliary belt sewn on the filter bag.
④ When unloading the filter cake, the cake unloading tool should be parallel to the filter cloth as far as possible to prevent damage to the filter bag.